The amount of malware-infected e-mails rose dramatically last month, according to reports from security researchers at MX Logic and Symantec. Advice to e-mail users: Be careful what you click.

The amount of e-mail-borne malware attacks jumped dramatically during the
month of September, according to security researchers at MX Logic and Symantec.
In its "October Threat Forecast & Report," security vendor MX Logic
reported that 5.14 percent of all e-mails in September contained
malware, more than twice August's percentage and more than five times
January's rate of 0.95 percent. Symantec had similar findings in its October
"State of Spam" report,
where the vendor reported the percentage of e-mails with malicious code
multiplied about 12 times between June and September.

"The two largest contributors to this increase in September were e-mails
purporting to be an iPhone game and fake FedEx delivery notifications," said
Sam Masiello, vice president of information security at MX Logic.

The fake
iPhone game is actually a Trojan, and the bogus FedEx delivery notification
e-mails attempt to trick recipients into opening a malicious .zip file
attachment. At its peak, the FedEx spam accounted for four out of five
malicious e-mail messages processed by MX Logic's Threat
Operations Center.
"It's unknown which group was sending out the fake FedEx notifications, but
it is believed to be the same group who sent out similar messages purporting to
be from both DHL [Worldwide Express] and UPS,"
Masiello said. "The malware for the fake iPhone games was named by the
major anti-virus vendors as being associated with the Srizbi botnet. Several
months ago, the Srizbi botnet accounted for more than 50 percent of all spam
being sent on the Internet. Although Srizbi is still prevalent, it has been
overtaken by the Cutwail/Rustock botnet as it relates to daily mail volumes."
The Symantec report also noted an increase of zombie activity by more than
100 percent between August and September, reversing a decline that occurred
between July and August. The countries with the largest increase in the number
of zombies include South Korea,
Kazakhstan, Romania
and Saudi Arabia.
However, both MX Logic and Symantec report the United
States still leads overall in spam sent.